Muffle kiln for the firing of glazed ceramic tiles

ABSTRACT

A muffle tunnel kiln for the firing of glazed ceramic tiles. It is furnished with lateral burners ranged in opposed pairs blow the muffled combustion chambers in such a way that the flames and combustion gases of said burners develop and are dispersed along honeycombed blocks of refractory material placed on the specially lowered decks of kiln cars under a stack of tile trays. The tunnel is thus heated not only by the usual muffled combustion chambers but also by the combustion gases of the lateral burners. The combustion gases circulate inside the tunnel, unlike those of the burners which heat the muffle combustion chambers.

Unite States am [15] 3,637,199

Poppi 1 Jan. 25, 1972 54] MUFFLE KILN FOR THE FIRING 10F 1,988,837 1/1935 Dressler ..263/28 GLAZED CERAMIC TILES Primary Examiner-John J. Camby [72] Inventor: Mauro Poppi, Via Pretorio 51, Sassuolo, ArtorneyRaymond A. Robic Italy 22 Filed: Mar.27, 1970 [57] ABSTRACT A muffle tunnel kiln for the firin of lazed ceramic tiles. It is 21 A 111123225 g g I 1 pp 0 furnished with lateral burners ranged in opposed pairs blow the muffled combustion chambers in. such a way that the [52] ILLS. Cl. ..263/28, 25/142 H flames and combustion gases of said burners develop and are [51] Int. Cl ..E27b 9/00 dispersed along honeycombed blocks of refractory material [58] Field of Search ..263/28;25/l42 R, 142 H, 142L placed on the specially lowered decks of kiln cars under a stack of tile trays. The tunnel is thus heated not only by the [56] References Cited usual muffled combustion chambers but also by the combustion gases of the lateral burners. The combustion gases cir- UNITED STATES PATENTS culate inside the tunnel, unlike those of the burners which 1,837,779 12 1931 Kneass, Jr ..263/28 heat the chambers- 2 Claims, ll Drawing Figure mrmummslsrz 333L199 INVENTOR Mauro POPPI ATTORNEY MUFFLIE lfllLN FOR THE FlRllNG 01F GLAZED CERAMIC TlLlES The firing of glazed ceramic tiles is at present effected in the industry by means of muffle-type tunnel kilns. The tiles are in troduced into the kiln or kiln cars bearing tile trays of refractory material; the tiles are laid flat on the tile trays without touching each other and the trays are then stacked one above the other.

Such tunnel kilns are of the muffle-type to prevent the combustion gases coming into contact with the glazed surfaces of the tiles; it requires only small deposits of fuel ash to reduce the market value of the tiles. Muffles cause firing to take place by heat irradiation, the inside of the tunnel being protected from the combustion gases.

The kiln cars run on rails like a sort of continuous train, entering the kiln at one end and leaving it at the other. As the chassis of the car must clearly be made of metal it is necessary to place a deck of refractory material of considerable thickness on the car to protect it from the heat and carry the tile trays. This refractory deck is, to all intents and purposes, a moving floor to the tunnel kiln.

The present invention relates to a muffle tunnel kiln of the type herein referred to, with means for accelerating the firing process and increasing the potential output of the kiln by 50 percent.

The invention is based on the principle of placing honeycombed blocks of refractory material on the refractory deck of the kiln car which are then heated by the flames from laterally placed oil or gas burners. To thisend it is best to reduce the thickness of the protective deck of refractory material on the kiln car so that the main dimensions of the kiln are more or less the same in cross section as those of a normal muffle kiln.

In other words, according to the invention, the superstruc ture of the kiln car is adapted and heated in such a way that the tile trays, and the tiles contained therein, are heated not only by the usual muffles at the side of the kiln but also by the kiln car itself, that is to say by that element in the kiln which usually absorbs rather than provides heat. The invention is illustrated, by way of example, in the accompanying drawing, which is a crosssectional elevational view of the left-hand half of a muffle kiln according to the invention. The right-hand section is not shown in the drawing as the two halves of the kiln are perfectly symmetrical.

As can be seen from the drawing a normal muffle tunnel kiln is furnished with lateral burners l with flame-spitting cones a and b. The flames are channelled between the blocks of honeycombed refractory material 2 which rest on the deck of the kiln cars 3. Again referring to the drawing, 4 indicates the refractory tile trays lying on the kiln cars 3. Five indicates one of the muffled combustion chambers which run parallel to the tunnel.

A gap 6 is left between the stack of the tile trays 4 (visible in the drawing) and the adjacent stack to the right (not visible, because it is symmetrical around the centerline A-B) through which gap a part of the combustion gases from the burner 1 passes. The gases thus pass through the blocks 2, rise up through the gaps 7 and above all 6 and circulate within the stack of tile trays.

The burners l are in pairs, one on the left and one on the right of the kiln car, and suitably spaced. The burners of each pair are placed opposite to one another.

As there is a relatively small volume of combustion gases emitted from the lateral burners, and as they cross a space (within the kiln) which is at a very high temperature, they leave no residue and therefore do not contaminate the surface of the glazes; to all intents and purposes the gases function as heat spreaders; for, whereas in normal muffle kilns a temperature of l,300 C. is required in the muffled combustion chambers if a firing temperature of 900 C. is to be reached, with this invention the temperature in the combustion chamber may be reduced by approximately 150 C. Furthermore, as the muffles are exposed to a considerably lower temperature they last much longer.

Preferably, of the total fuel consumed (oil, producer gas,

natural gas) percent is used in the muffled combustion chambers and 10 percent is used by the lateral burners l.

The combustion air of the lateral burners 1 may be divided into two parts: that which is used to inject the flames and that which is used to feed the flames. That used to feed the flames is conducted to the burner from inside the tunnel by means of flues and passages built into the refractory material below the muffle shelf, or in any other way through fit.

It should be noted that it is possible to have one lateral burner l on while that opposite to it is off; in this way turbulences are created in the tunnel of the kiln which increase considerably the efficiency with which the available heat is circulated.

Those parts of the drawing that are not numbered are parts which occur, as illustrated in the drawing, in tunnel kilns of the type most widely used in the industry today.

I claim:

1. A kiln for firing glazed ceramic tiles comprising a tunnel,

blocks of refractory material for passing through said tunnel,

kiln cars for transporting the said blocks in the tunnel, muffles for circulating combustion gases for the supplying the majority of the heat to the tunnel, lateral burners located below the muffles for supplying directly a small quantity of heat in the tunnel, the temperature of the heat of the burners being higher than the one of the muffles.

2. A kiln as recited in claim 1, comprisingrefractory tile trays stacked on the cars for providing gaps therebetween so as to let the combustion gases circulate freely. 

1. A kiln for firing glazed ceramic tiles comprising a tunnel, blocks of refractory material for passing through said tunnel, kiln cars for transporting the said blocks in the tunnel, muffles for circulating combustion gases for the supplying the majority of the heat to the tunnel, lateral burners located below the muffles for supplying directly a small quantity of heat in the tunnel, the temperature of the heat of the burners being higher than the one of the muffles.
 2. A kiln as recited in claim 1, comprising refractory tile trays stacked on the cars for providing gaps therebetween so as to let the combustion gases circulate freely. 